title: Combined subthreshold dose inhibition of myosin light chain phosphorylation and MMP-2 activity provides cardioprotection from ischaemic/reperfusion injury in isolated rat heart.
abstract: OBJECTIVE
  Phosphorylation and degradation of myosin light chain 1 (MLC1) during myocardial ischaemia/reperfusion (I/R) injury is a well-established phenomenon. It has been established that MMP-2 is involved in MLC1 degradation and that this degradation is increased when MLC1 is phosphorylated. We hypothesized that simultaneous inhibition of MLC1 phosphorylation and MMP-2 activity will protect hearts from I/R injury. As phosphorylation of MLC1 and MMP-2 activity is important for normal heart function, we used a cocktail consisting combination of low (subthreshold for any protective effect alone) doses of MLC kinase, MMP-2 inhibitors and subthreshold dose of an MLC phosphatase activator.
  
  
  METHODS
  Isolated rat hearts were subjected to 20 min of global, no-flow ischaemia and 30 min reperfusion in the absence and presence of inhibitors of MLC1 phosphorylation and degradation.
  
  
  RESULTS
  The recovery of cardiac function was improved in a concentration-dependent manner by the MLC kinase inhibitor, ML-7 (1-5 μM), the MLC phosphatase activator, Y-27632 (0.05-1 μM) or the MMP inhibitor, doxycycline (Doxy, 1-30 μM). Co-administration of subthreshold doses of ML-7 (1 μM) and Y-27632 (0.05 μM) showed a potential synergistic effect in protecting cardiac contractility and MLC1 levels in I/R hearts. Further combination with a subthreshold concentration of Doxy (1 μM) showed additional protection that resulted in full recovery to control levels.
  
  
  CONCLUSIONS
  The results of this study exemplify a novel low-dose multidrug approach to pharmacological prevention of reperfusion injury that will enable a reduction of unwanted side effects and/or cytotoxicity associated with currently available MMP-2 and kinase inhibiting drugs.
authors.affiliation: Department of Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada.
authors.forename: Virgilio J J
authors.initials: VJ
authors.lastname: Cadete
authors.forename: Jolanta
authors.initials: J
authors.lastname: Sawicka
authors.forename: Lane K
authors.initials: LK
authors.lastname: Bekar
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Sawicki
mesh_terms: D000577:Amides / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001381:Azepines / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004318:Doxycycline / Q000008:administration & dosage / Q000494:pharmacology; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000187:drug effects / Q000378:metabolism*; D061965:Matrix Metalloproteinase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy* / Q000503:physiopathology; D018994:Myosin Light Chains / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009281:Naphthalenes / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011725:Pyridines / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000577:Amides; D001381:Azepines; D002316:Cardiotonic Agents; D004791:Enzyme Inhibitors; D061965:Matrix Metalloproteinase Inhibitors; D018994:Myosin Light Chains; D009281:Naphthalenes; D011725:Pyridines; C076659:myosin light chain I; C070571:ML 7; C108830:Y 27632; D009219:Myosin-Light-Chain Kinase; D020778:Matrix Metalloproteinase 2; D004318:Doxycycline
keywords: MLC kinase; MLC phosphatase; matrix metalloproteinase; myosin light chain; phosphorylation